I'm so not looking forward to this winter, and it's not just because we've had such a lousy summer that it feels like we've gone straight from spring to autumn with nothing in between. No, I'm not looking forward to it because I know that every time I want to turn the central heating or the gas fire on I'm going to have to think twice. And I'm someone who feels the cold.

Environmentally speaking of course, that's a good thing; the more of us who can resist the urge to turn up the thermostat the better, as far as helping to save the planet goes. And while I may be slightly uncomfortable huddled over my laptop wrapped in an extra jumper and a pair of fingerless gloves, at least I know that when the temperature plummets to an unbearable degree I can and will flick that switch. But there are millions of people living in this country who simply don't have that option: millions of people for whom this coming winter spells abject misery as they struggle with the conundrum of whether to buy food for the table or respite from the chill.

According to the government's somewhat conservative estimate, there are currently 2.5 million people living in fuel poverty, that is, 2.5 million people who are paying out more than 10% of their incomes for the luxury of lighting and heating their homes: as the cost of energy soars, that number is set to get even higher.

And yet there's an easy answer to all this. For while the British public is being forced to scrimp and save, to tighten our belts in readiness for the exorbitant winter heating bills, the energy companies and their shareholders are wallowing in obscene piles of money, all thanks to the gargantuan profits they've made from the rising price of oil. It doesn't take a genius to work this one out, surely?

The energy companies are enjoying windfall profits: it's time they paid that windfall tax.

The money a windfall tax would generate would be more than enough to help out pensioners, the low paid, and anyone else facing fuel poverty and a miserable winter ahead. However, according to the chancellor Alistair Darling there are "problems of principle and practicality" with this idea; and as far as Gordon Brown is concerned it's too "risky". Apparently today's Labour government is so in thrall to big business and multi-national conglomerates that it would rather see the elderly and vulnerable suffering hypothermia just like in the good old days than jeopardise its warm and glowing relationship with the money men. Keir Hardie must be turning in his grave.

The campaign for a windfall tax on energy companies' excessive profits is gathering speed, with an Observer-YouGov poll showing two-thirds of voters and even 57% of Tory voters support it, along with 70 MPs. It's hardly surprising there is outrage at their record profits, up six-fold in three years, while prices rise by as much as 35%.

There's outrage indeed, especially when a company like British Gas hoiks up its prices with a record-breaking increase one day, and then the next day announces higher than expected profits. In the first half of the year its parent company Centrica made close to £1bn, out of which it rewarded its shareholders with a 16% rise in their dividend payments. This is the ugly face of capitalism, the one that sees the rich getting richer and the poor staying poor: that it's happening under a Labour government, and that that government can see nothing wrong with it, should disabuse anyone of the notion that the Labour party of the 21st century is now anywhere close to being a party of the left.

Tim Worstall argues that a windfall tax will scare away potential investors, and that start-up companies looking to get a foothold in the energy industry will think again when they realise their "hard-earned" dosh could be up for grabs. But a windfall tax is just that, it's a one-off tax designed to be used when companies make well in excess of their expected gains; it's not an annual skimming off of monies, and it happens so rarely in this country that any potential investor can rest assured that future profits will be theirs to keep. And I don't think even Compass is suggesting that all profits should be going to the government. These people will still be making money: just not as much as they'd anticipated.

The Compass campaign for a windfall tax that helped to kick-start this debate has growing support from both parliamentarians and the public. As well as the 70 MPs that Toynbee mentions, senior trade union officials and thousands of ordinary British citizens have signed the petition calling on the government to adhere to its principles of social and environmental justice; even ministerial aides are coming out in support of it. The tax is set to be discussed by delegates at both the Labour party conference this autumn, and at the Trade Union Congress (pdf) in a couple of weeks' time. So whether Brown and Darling like it or not, this one's not going to go away.

After the disappointment of his first year in office, and amid calls for yet another leadership election, Brown needs a vote-winner like this. Instead of the half-measures he appears to be considering, like charging the energy industry an extra £100m a year, which is better than nothing but nowhere near the amount a windfall tax would garner, and instead of struggling to find excuses as to why and how it can't be done, he should be looking at the books and finding a way to make it work. The public wants it, his MPs want it, even a majority of Conservatives want it. But what should hold even more sway is that the poor and the vulnerable need and want it: indeed, there are some who won't be able to see out this winter without it.